This invention relates to an improved method for managing volumes in a storage system.
The amount of data that is handled by a firm of the present day is increasing, together with the increase of storage capacity of the storage system. While the capacity of the storage system increases, rather than the volumes in a storage system won't have a homogenous performance but each of them will have a variety of performance levels, respectively. The optimum strategy of layout design of volumes to be used to store data based on the importance is required. In addition, since the importance of data is not always at a certain level, moving data between volumes having different performance is often needed.
Moving data between volumes is done in general by copying data from the source volume to the destination volume. In this case the data that exists in the destination volume is overwritten. The destination volume should be selected which must be an unused volume (the volume that stores only unnecessary data). Because of this, the storage management strategy with the assumption of moving data being anticipated requires for the system to have always an empty, blank volume to be served as a new destination of data. Always having a bunch of blank storage volumes to be served as the new destination volumes may be wasting the resource, and a high performance spare set of disk drives among other things not used for the routine work is not desirable in view of cost saving.
In contrast to this, JP 2002-32197 A suggests a method for exchanging data between the source volume and the destination volume for the purpose of moving data between volumes. According to this method the data can be moved without overwriting existing data on the destination volume. In this prior embodiment, two extra volumes are provided for temporary data backup in addition to two principal volumes from and to which the data is exchanging, to copy data from two principal volumes exchanging data to the temporary backup volumes, then to copy the data backed up in the temporary volumes to their respective destination volumes. According to this method, moving data is available even when the destination volume is not empty, if only two temporary backup volumes are provided.